When presented with a tool or a device, we assess its features and attributes to understand what we can do with it, i.e., its perceived affordances. Visual inspection alone cannot convey all of this information and it is often necessary to feel an object to gain a fuller understanding of its material and structural properties. These qualities are perceived through tactile stimulation (e.g., on skin) and kinesthetic receptors (e.g., in hands). When an object is deformed, a rich set of sensations come into play to inform a user about its internal structure. For example, when reading a paper document, the physical structure of pages can help guide a user to particular locations in the document. A book can have physical tabs to indicate chapters and its pages might have “dog ears” to denote bookmarks or creases at frequently read passages. The distribution of pages between the hands of the user provides haptic representation of the current reading location. Pages sliding between the user's fingers provide feedback on the speed with which the user is navigating.
However, many, if not all, of these haptic affordances are lost when navigating documents on rigid devices such as smartphones and tablet PCs. When designing flexible organic user interfaces, the structural qualities of the device are inherited from the material of the substrate used in its construction. While haptic technologies have been used to mimic textures of different materials, these technologies often focus on surface features.